基于大涡模拟超大直筒-锥段型钢结构冷却塔极值风压研究

摘要

以国内拟建的首座超大直筒-锥段型钢结构冷却塔(189 m)为例,通过大涡模拟法获得其表面三维气动力时程和周边流场分布形态,并与国内外实测及风洞试验结果对比验证了数值模拟结果的有效性.在此基础上,基于三种典型风压极值算法(峰值因子法、改进峰值因子法和Sadek-Simiu法)对比分析了此类钢结构冷却塔表面峰值因子和风压极值的分布规律,并基于非线性最小二乘法分别给出了直筒和锥段部分的风压极值一维/二维拟合公式及取值建议;研究表明:直筒-锥段型钢结构冷却塔负压极值区和分离区附近风荷载呈现明显的非高斯特性,基于高斯分布假定的峰值因子法计算得出的极值风压数值偏小;锥段和直筒段背风面极值风压均大于规范取值,锥段迎风面和侧风面极值风压与水工规范极值接近,而直筒段迎风面和侧风面极值风压与荷载规范极值接近;所提出的风压极值拟合公式可以包络直筒和锥段的实际风压极值,最大误差＜10％.研究结论可为此类钢结构冷却塔风荷载设计取值提供参考.%Taking a domestic super large steel cylindrical-cone cooling tower (189 m) to be constructed as an example,numerical wind tunnel tests were conducted based on large eddy simulation (LES) to get 3-D aerodynamic force histories on its surface and flow-field distribution state around it.Comparing the numerical simulation results with those of field measurements home and abroad and actual wind tunnel tests,their correctness and effectiveness were verified.Furthermore,the traditional peak factor method,the improved peak factor one and Sadek-Simiu one were employed to analyze the peak factor and the extreme wind pressure of this cool tower contrastively.The 1-D and 2-D fitting formulas for the extreme wind pressures of cylinder and cone parts of the tower and suggestions of value-selecting were deduced based on the non-linear least square method.The study showed that the wind loads on the cool tower's surface negative pressure extremum zone and near the separation zone reveal obvious non-Gaussian features;the extreme wind pressure values calculated with the peak factor method based on Gaussian distribution are smaller than the specified value in the code;the extreme wind pressures at leeward side of cylinder part and cone part are greater than the specified value in the code;the extreme wind pressures at windward side and lateral wind side of cone part are close to the specified value in the code GB/T 50102-2014,while the extreme wind pressures at windward side and lateral side of cylinder part are close to the specified value in the code GB 50009-2012;the calculated results with fitting formulas for extremum wind pressure proposed here agree well with those actually measured on the tower;the main conclusions obtained here provide a reference for wind loads design of this type cool tower.